1. Field of the Invention
The present invention relates generally to medical endoscopes and, more particularly, to an endoscope having a resistance heater.
2. Prior Art
Medical endoscopes are used for insertion in damp and warm body cavities, while they themselves retain the cooler room temperature. This results in the endoscope becoming misted, which is particularly annoying in the case of a window provided on the endoscope, because the misting impedes visibility through the window.
It has therefore been known for some time, to heat the window in order to prevent misting. Apart from other heating methods, such as those using light, hot gas or hot liquid, generally electric resistance is mainly used, which is located close to the window in the endoscope.
For example, U.S. Pat. No. 4,076,018 shows an endoscope having a window looking out to the side, against which is positioned a heating conductor. U.S. Pat. No. 4,076,018 also mentions other possibilities, such as a heating coating on the window.
US 2007/0149856 A1 shows an endoscope, where a heating ring is positioned in the area between the window and a system tube, which accommodates the optical system and is located within the fiber tube. US 2007/0149856 A1 also shows a temperature control sensor located adjacent to the window.
JP 2006000282 shows an endoscope, where a heating coil is arranged around the edge of the window.
The known designs fulfill their purpose of keeping the window mist-free, but have design disadvantages. The arrangement of the heating device close to the window makes the design of the endoscope, which is in any case very constricted, even worse. It is also particularly difficult to ensure adequate thermal contact between the heater and window.